Links and invites will follow. Start trying at http://wave.google.com/ -- There's a link to request an invite near the bottom.
The link to the Long YouTube is about an hour long from last spring -- the Google Web Developer Preview

I have about 40 invites to Google Wave, add an email on my page if you want an invite -- CasperSchmidt

I really hope this takes off. It's from Google and there is a lot of hype surrounding it, but I can definitely see the utility. I'm constantly seeing e-mail being used as a collaboration utility -- someone will write up an email describing a problem or a feature request or whatever which is then followed by fifty or so one-line responses with mixed bottom, top, and inline posting, sometimes modifying the original e-mail text. I've tried to get people to use more appropriate tools, but I bet anyone here can guess how successful that was. I can't imagine I'm the only one who sees this kind of thing.

Just remember that with the richness of complexity, also comes the complexity of complications, errors, limitations, restrictions and difficulties of use. Not everyone will want the learning curve, or be able to understand all the is involved. KeepItSimpleStupid can be much quicker and have far fewer headaches.

GoogleWave crushed under its own weight. Perhaps the acquisition of Ether Pad should have been a major move by Google instead of a minor move of adding it to GoogleWave.

April 2011, GoogleWave still exists but is in a dormant stage like it's not longer developped as a separated service and you must now have an GoogleAccount? to enter the service. The good thing about this is that all the PR people are staying away and you find some great Waves about education still on it.--PieterJansegers